Installations comprising a plurality of auto-generators producing hot gas under pressure



3,011,484 GENERATORS 2 Sheets-Sheet 1 H. HORGEN Dec. 5, 1961INSTALLATIONS COMPRISING A PLURALITY OF AUTO- PRODUCING HOT 'GAS UNDERPRESSURE Filed March 10, 1960 INVEA/ TOR f/i/y: ar bw BY 4 ATTORNEY H.HORGEN 3,011,484 INSTALLATIONS COMPRISING A PLURALITY OF AUTO-GENERATORSFiled March 10, 1960 PRODUCING HOT GAS UNDER PRESSURE 2 Sheets-Sheet 2LIN ATTORNEY 3,011,484 INSTALLATIONS COMPRISENG A PLURALITY OFAUTO-GENERATORS PRODUCING HOT GAS UNDER PRESSURE Helge Hot-gen, Lyons,France, assignor to Societe d- Etudes et de Participations Eau, Gaz,Electricite, Energie S.A., Geneva, Switzerland a Swiss society FiledMar. 10, 1960, Ser. No. 14,151 Claims priority, application France Mar.18, 1959 Claims. (Cl. 123-46) The present invention relates toinstallations comprising a plurality of auto-generators, producing hotgas under pressure for supplying a receiving machine, more particularlya gas turbine; and it concerns more particularly but not exclusive,among such installations, those in which the auto-generators arefree-piston auto-generators.

It should be noted here that by auto-generator is understood a machinecomprising, on the one hand, an internal combustion driving part,preferably operating on the two-stroke Deisel cycle, and, on the otherhand, a compressor part, the output of which in the form of compressedair is used, at least for its greater part, for supercharging andscavenging the driving part, from the exhaust ports of which issue thehot gas under pressure the production of which is the object of theauto-gener- I ator.

The object of the invention is above all to render installations of thekind above specified such that they meet the various requirements ofpractice better than heretofore.

The invention consists principally in establishing, at least for lowloads, a communication between two compressor cylinders of at least twoauto-generators for at least a part of each period of their workingcycles during which different pressures prevail in these cylinders, suchthat there is obtained a transfer of air from one of the cylinders tothe other and a corresponding reduction of the output of each of them,the magnitude of this transfer being advantageously adjustable either,for a given phase diiference, by a variation in the resistance opposedto this transfer by the communication conduit, or, for a fixedresistance of said conduit, by a variation of the phase difierencebetween the auto-generators, or by a simultaneous variation of theresistance of the communication conduit -and of the phase differencebetween the auto-generators.

Preferred embodiments of my invention will be hereinafter described withreference to the accompanying drawings given merely by way of exampleand in which:

FIG. 1 diagrammatically shows an installation comprising twoauto-generators having their outputs connected with a common gasturbine, the injection pump and the means for regulating the delivery ofthis pump being shown for only one of these auto-generators.

FIG. 2 diagrammatically showns a modification intended to facilitate thestarting of the auto-generators of the installation shown by FIG. 1.

FIGS. 3 and 4 diagrammatically show two dilferent positions of theregulating element of the device shown in FIG. 2.

FIG. 5 shows another modification of the installation shown in FIG. 1.

FIG. 6 is a diagram intended for explaining the operation of themodification shown in FIG. 5.

FIG. 7 is yet another modification of the installation shown in FIG. 1.

FIG. 8 serves to illustrate the operation of the modification shown inFIG. 7.

FIGS. 9a, 9b, 9c illustrate the effect of a modification of phaseditference between two auto-generators 3,dll, l84 Patented Dec. 5, 1961of an installation constructed according to the invention.

The installations shown by the drawings comprise two free-pistonauto-generators and a gas turbine fed with power gas from saidauto-generators.

Each of these auto-generators A and B comprises, in conventional manner,an internal combustion engine cylinder 1, two compressor cylinders 2,arranged on either side of the cylinder 1, and two stepped pistons 3,each of which comprises an internal combustion engine piston element 3aand a compressor piston element 3b. These two pistons have opposedmovements and are connected together by a synchronization device, notshown, piston elements 3a operating as opposed pistons in cylinder 1, ofwhich they control the inlet ports 4 and the exhaust ports, not shown,while the compressorpiston elements 311 each operate in their respectivecylinder 2, which they divide into an internal chamber 2a and anexternal chamber 2b. Chamber 2a forms the compressor chamber proper andfor this purpose, it is provided on the one hand with suction valves 5,which draw air from a suction casing 6, advantageously common to both ofthe auto-generators and in communication with the surrounding air, andon the other hand, delivery valves 7, through which the air compressedin chamber 2a is forced, during every inward stroke of pistons 3, into acompressed air casing 8 surrounding the combustion cylinder 1. Therespective casings 8 of the two auto-generators A and B can communicatewith each other through a conduit 9 or may also be separated from eachother, as is indicated diagrammatically, by a closure plate 10 shown indotted lines.

The external chambers 2b of the two cylinders 2 form return pneumaticpower accumulators called cushions which, during every' outward strokeof pistons 3, store up the energy liberated by the combustion of thefuel in cylinder 1 and converted into kinetic energy during the outwardstroke of said pistons, in order subsequently to restore this energy, atleast in a large part, to said pistons for ensuring the next inwardstroke thereof, during which takes place the compression of the airwhich, during the preceding stroke, has entered chambers 2a throughsuction valves 5, as well as the compression of the combustion air whichhas entered the cylinder 1 through the ports 4.

To ensure stable operation of the auto-generators despite variations inthe lengths of stroke of pistons 3 and in the pressures at which air iscompressed in chambers 2a and forced into casing 8, the mass of airsituated in cushions 2b is regulated by a known device called sta- Ibilizer 11. This device, provided with non-return valves 11a, 11b andaxially movable in a cylinder 12, ensures when moved downwardly theadmission of air from casing 8 to cushions 2b through openings 13 andconduit 14, and when it is moved upwardly the outflow of air from thecushions through the same conduit 14 and openings 15. In its middleposition, on the contrary (shown in FIG. 1), it interrupts thecommunication between the cushions and the casing. The movements of-thisstabilizer are controlled by a stepped piston 16, the various faces ofwhich are subjected to the action, on the one hand, of the pressureprevailing in the casing 8 and supplied by a conduit 17 to the face 16aof piston 16, on the other hand, of the mean pressure prevailing in thecushion and supplied by conduit 18, throttled at 19, to the space underthe face 16b of said stepped piston 16, and finally of a pressure takenfrom the cushion 2b at moments adapted to be controlled from theoutside, and supplied through a valve 20, controlled from the outside,and through a conduit 21 to the face of stepped piston 16. Finally, thestabilizer is also under the action of a spring 22, preferablyadjustable.

It should be noted that all these details relating to the control of thestabilizer are given by way of example and may be modified in variousways, using for example, in place of the mean pressure acting on theface 16b of stepped piston 16, a pressure taken from the cushion for apredetermined position of piston elements 3b in compressor cylinder 2.

With regard to the injection of fuel into the cylinder 1, this iseffected by one or more injectors, not shown, fed by an injection pump23, the regulating rod 24 whereof is controlled for example by apressure called modulated pressure, which acts on a piston 25 coupled tothe rod 24 by means of a cam lever 26, the magnitude of said pressurebeing determined by the speed governor 27 driven by the turbine 28 ofthe installation, said turbine being supplied with power gas byauto-generators A and B.

The movements of rod 24 are limited by a stop 29 interposed between thetwo cam surfaces 30a and 30b of lever 26 and which is controlled by anoperating factor of the corresponding auto-generator, for example by themean pressure in cushions 2b or by an analogous pressure, this pressurebeing supplied by a conduit 18a to the space under a piston 31 on whichstop 29 is mounted.

To ensure the supply of power gas to turbine 28, the exhaust ports (notshown) of combustion cylinders 1, when pistons 3 are in the vicinity oftheir outer dead points, are placed in communication with a power gasmanifold 32 connected to the inlet of turbine 28'by means not shown indetail.

Installations of the kind above described necessitated, at low loads,where the intake pressure of the turbine is reduced, the exhausting of acertain quantity of compressed air or gas produced by theauto-generators, since the minimum output of these auto-generators-whichoutput is determined by the necessity for opening, on every outwardstroke of the pistons, the inlet and exhaust ports of the combustioncylinder-is higher than the gas requirement of the turbine. This exhaustof compressed air or gas obviously entails an appreciable loss.Furthermore, it is accompanied by an unpleasant noise. It has alreadybeen proposed to reduce this loss by recycling a part of the surpluscompressed air to the inlet of the compressor cylinder. This recyclingalthough appreciably reducing the loss of energy, was likewise noisy andnecessitated the provision of special suction conduits withsound-absorbing means and heat insulation.

The disadvantages of the known constructions are eliminated, at least inlarge part, by the main feature of the present invention which consistsin providing, at least for low loads, a communication between at leasttwo of the compressor chambers 2a of the two autogenerators A and B forat least part of each period of their working cycle during whichdifferent pressures prevail in these cylinders, such that there is atransfer of air from one of the cylinders to the other. Preferably andto obtain conduits of minimum length, this communication is providedbetween the two compressor cylinders which are situated at the same endof the two auto-gem erators A and B arranged side by side.

Thus, in the installation shown in FIG. 1, there is provided on theright and left of the two auto-generators A and B a communicationconduit 33 connecting the two compressor chambers 2a provided at theseends.

For regulating the magnitude of the transfer from one chamber 2a of eachpair to the other, various means may be employed. It is assumed first ofall that the two auto-generators A and B are maintained at a constantphase difference of 180 by means to be described hereinafter. In such acase, it is merely necessary to provide, in the communication conduits33, means which by throttling or more or less complete closure producein the conduits 33 a variable resistance to the flow of the transferredair. These means effect a greater reduction in the cross-section ofconduits 3-3 as the load of the installation increases, and close theseconduits completely (the resistance to transfer then becomes infinite)when the load becomes at least equal to the value for which turbine 28can absorb the whole amount of gas supplied by the auto generators. Oncethese conduits 33- are fully closed, the installation works in the usualmanner solely by regulation of the quantity of fuel injected into thecombustion cylinders as a function of the speed of turbine 28.

With regard to the means for controlling the crosssection area of thepassage through-conduits 33, they may have, for example, the form ofslide-valves 34. in the installation shown in FIG. 1, a rod 35 connectstogether the two slide-valves 3 4 which control the crosssection areasof the two conduits 33 connecting together the respective cylinders 2 ofauto-generators A and B that are located at the same ends of saidgenerators, and these two slide-valves are controlled in response tovariations of a factor the magnitude of which depends upon the loadunder which the installation is operating, the control being such thatthe cross-section area of the conduits 33 is greater as said load islower, and that conduits 33 are fully closed as soon as this loadexceeds a predetermined value, corresponding to a mean value of the loadof the installation. To control slide-valves 34, a rod 35a connects themto a piston 36 subjected to the action of a force the magnitude of whichis a function of the load of the installation. For example, this forceis exerted by a liquid placed under pressure by a governor 27 driven byturbine 28, said liquid being sent through a conduit 37, on the one handto piston 36 and, on the other hand, to piston 25 controlling thefuel-regulating rod 24. To reduce the force required to moveslide-valves 34 it is advantageous to balance the pressures acting onopposite sides of each slide-valve. For this purpose the end of eachslide-valve 34 opposite to that more or less deeply engaged in thecorresponding conduit 33 is slidable in a cylinder 34a, and the samepressure is caused to act in this cylinder as that existing in thetransfer conduit 33. To obtain this result it suifices to provide agroove 3'41) in the surface of piston 34, said groove constantly placingcylinder 34a in communication with conduit 33.

Preferably, transfer conduits 33 are situated inside the suction casing6 of the auto-generators, which considerably reduces the noise resultingfrom the flow of air through said conduits.

In view of the fact that the cross-section area of the passage throughconduits 33, even when the slide-valves are in their maximum openingposition, has a limited value, it is not possible to reduce to Zero theoutput of the pair of auto-generators, even when conduits 33 are fullyopen. Furthermore, such zero output would be by no means desirable inview of the fact that the internal combustion engine portions of theauto-generators always require a certain quaitity of scavenging air, butby means of the installation, it is possible to obtain a considerablereduction in the total flow of air at very low pressures. Consequently,an installation according to the invgntion has a very economical fuelconsumption at low When it is desired to increase the output of theautogenerators, the cross-section area of the passage through conduits33 is gradually reduced. Closing of these conduits is effected forexample when the pressure of the power gas at the turbine inlet has avalue of from 1.5 to 2 kg. per sq. cm. above atmospheric pressure. Forhigher pressures, the output of the auto-generators may be adaptedautomatically to the turbine demand without it being necessary to openconduits 33.

To maintain the two auto-generators forming part of the installationshown in FIG. 1 a phase difference of any appropriate means may beemployed, for example for this purpose a device is used such as thatshown in the left-hand part of FIG. 1 and comprising a contactor arm 38,driven at a definite speed for example by means of an electric motor,not shown, and which, in two of its positions at 180 to each other,closes for a short time, by

means of brushes 3 9 and 45]), the circuits 41 and 42of two coils 43, 44acting on valves 20 included, for each of the two auto-generators A andB, in the conduit 21 which, when the corresponding valve 20 is open,allows the pressure prevailing at that moment in cushion 2b to act onthe face 16c of stepped piston 16. The number of revolutions ofcontactor arm 38 per unit of time corresponds to the number ofoscillations of the opposed free pistons of each of the auto-generatorsduring the same time, and the angular offsetting of brushes 39 and 40,which is 180 in the installation of FIG. 1, determines the phasedifference between the cycles of operation of the two autogenerators, asdescribed in detail in my US. patent application Ser. No. 777,056, filedNovember 28, 1958, for Control Means for Free-Piston or Semi-PistonEngines.

Installations having a plurality of auto-generators as shown in FIG. 1are generally started with the generators in phase, and it is only afterstarting that the desired phase difference is produced between themovements of the pistons of the auto-generators. As long as the twoauto-generators of the installation shown in FIG. 1 operate withoutphase difference, after their starting, the compressed air outputs andhence the gas outputs of the autogenerators are unaffected by theposition of slide valves 34 so that, at this moment, conduits 33 my bewide open. Consequently, the pressure in the conduits leading to theturbine would rise very rapidly and the auto-generators would stop ifsteps were not taken to discharge their outputs during this period ofrunning with Zero phase difference. To ensure such a discharge as longas the autogenerators are running in phase, according to a particularlyadvantageous embodiment of the invention, each of the conduits 33 isbrought into communication with the surrounding air, or better stillwith the suction casing, and this communication with the surrounding airor with the suction casing is closed only when the desired phasedifierence between the auto-generators is obtained.

A particularly simple device for obtaining this result isdiagrammatically shown in FIGS. 2 to 4. According to these figures, thecommunication conduit 33 between two compressor chambers 2a comprises anoutlet orifice 45 which, when disengaged, connects conduit 33 directlywith the interior of the casing 6. In this case, a hole 46 is providedin slide-valve 34-. When this slide-valve is in the positioncorresponding to the starting of the autogenerators (see FIG. 2), itopens not only conduit 33 but also outlet orifice 45, so that during thestarting period, the compressed air in the compressor chambers 2a isrecycled through conduit 33 and orifice 45 into the suction casing. Atthe end of the starting period and after the de sired phase differencebetween the cycles of operation of the auto-generators has beenobtained, slide-valve 34 is moved to the position shown in FIG. 3. Inthis position, the slide-valve closes outlet orifice 45, but stillleaves conduit 33 open through the hole 46 provided in said slide-valve.The more slide valve 34 is moved toward the left in FIG. 3, the smallerdoes the cross-section of passage through conduit 33 become. When theload on the installation has reached the value from which the turbine iscapable of receiving all the gases produced. by the auto-generators innormal running conditions, that is to say without any recycling or othermeans capable of reducing the output, slide valve 34 is moved into theposition shown in FIG. 4, where this valve completely closes thecommunication between the compressor chambers 2a of the auto-generators.

, In certain cases, the application of the chief feature of the presentinvention permits a considerable simplification of the entire regulationsystem of the installation. Such a simplified system is shown in FIGS. 5and 6, this system being applied to an installation having twoautogenerators operating with a phase difference of 180. It is assumedthat the installation has a power which variesonly within definitelimits, which are above the 'Zone of low powers, for which the turbinecould not absorb all the gases produced by the auto-generators in normalworking conditions. In this case, it suifices to open conduit 33 onlyfor starting the installation. Thus, slide-valve 34, which controlsconduit 33, can occupy only two positions, one for which it completelycloses conduit 33 (position shown in FIG. 5) and the other for which itcompletely opens conduit 33. For this purpose, there is inserted in theconduit 47, supplying any fluid under pressure to the piston 36 whichcontrols slide-valve 34, a three-way cook 48 which, in one of itspositions (that shown in FIG. 5), allows the fluid under pressure to acton piston 36, causing slide-valve 34 to move to its closing position,while, in another position, cock 48 puts conduit 47 into communicationwith the surrounding air, whereby the spring 49 acting on piston 36 canreturn the slide-valve to the position for which it fully opens conduit33.

The operation of an installation such as shown in FIG. 5 is illustratedby the diagram of FIG, 6, where the abscissae are the pressures p of thepower gas supplied by the auto-generators, these pressures beingproportional to the power which the installation is to deliver, whilethe ordinates are the outputs D of power gas of said autogenerators.Line I shows the minimum outputs of the auto-generators as a function ofthe pressures p, while line II shows the maximum outputs of theauto-generators as a function of the pressures, the minimum outputsbeing those obtained without recycling.

Normally, the installation operates according to curve III betweenpoints 1 and 2. It will be seen that for all the points of this curveIII, the output D for different pressures p is always between lines Iand II, and can therefore be supplied without recycling or other meansof reducing the normal output of the auto-generators. Consequently, theinstallation operates between these points 1 and 2 with slide-valve 34closed. Only for starting and for idling, when the output capable ofbeing absorbed by the turbine is indicated by the point 0, isslide-valve 34 opened wide, which reduces the power gas supplied by thetwo auto-generators to the output indicated by the said point 0. Afterthe starting period, conduit 33 is closed by means of slide-valve 34.The pressure and quantity of power gas from the auto-generators thenincrease very rapidly, until one of the points of curve III between itsends 1 and 2 is reached, said point corresponding to the turbineconsumption. Any regulation is effected henceforward normally, solely byvariation of the quantity of fuel injected, by means of rod 24, which iscontrolled by the same means as those already described for theinstallation of FIG. 1.

It should be noted that, in this installation, intermediate powersbetween points 0 and 1 cannot be obtained.

It should be noted that in an installation according to FIG. 5, it issufficient to provide the communication conduit 33 and its slide-valve34 on one side only of the two auto-generators, that is to say, forexample, only between the two compressor chambers at the right-hand endsof the auto-generators. It is true that, during starting and idling,there is produced a slight inequality between the pressures prevailingin the compressor chambers on opposed sides of each auto-generator, butthis inequality is necessarily slight, since the air pressure is low inthe periods during which it exists. This inequality can be readilysupported by the synchronization mechanism which, in each of the twoauto-generators, connects the two opposed free pistons together.

Of course, in an auto-generator installation as shown in FIG. 5, it isalso advantageous to arrange the communication conduit 33 and its slidevalve 34 inside the suction casing 6 which is preferably common to thetwo compressor chambers connected together by conduit 33.

Another simplified system of regulation, applicable to the cases wheretwo auto-generators operate with a phase difference of is shown in FIG.7 and its mode of operation is illustrated by FIG. 8.

The arrangement of FIG. 7 is applicable to the case where theauto-generators operate almost always at their maximum power, or to thecase where fuel consumption is of secondary importance whereas thesimplification of the installation is of primary importance. In theinstallation shown in FIG. 7, the output of power gas is regulatedthroughout the entire range of different powers by greater or lesseropening of conduit 33- which connects the two compressor chambers 2atogether. Slide-valve 34 completely closes conduit 33 only when maximumpower is reached. The slide-valve is controlled by the pressure of afluid, which pressure varies with the load of the installation, and canbe produced by a governor 27 driven by turbine 28.

Regulation of the quantity of fuel injected into the power cylinders ofthe auto-generators is effected, according to FIG. 7, by an internalcontrol factor of the auto-generators, for example by the pressure incasing 8 of each auto-generator. Thus, according to FIG. 7, lever 26a,which controls the regulating rod 24 of injection pump 23, is actuatedby a piston 59 one face of which is under the action of the pressureprevailing in casing 8 and admitted to the piston 50' through a conduitStia, while the other face is under the action of an opposing spring 51.To give lever 26a and hence rod 24, for every pressure prevailing incasing 8, a definite position, the head 52 of the rod 53 of piston 49cooperates practically Without backlash with a slot 54 provided in lever26a and having a suitable shape and slope.

The operation of the installation shown in FIG. 7 is illustrated by FIG.8. In this figure, the abscissae and ordinates as well as curves I andII have the same signification as in FIG. 6. In addition, in FIG. 8,curve IV shows the outputs D of gas necessary for driving the turbine asa function of the pressure p. Finally, curve V indicates the output ofthe auto-generators as a function of the pressure when the fuelinjection is regulated by the device shown in FIG. 7, and comprisingmore particularly piston 49, the head 52 of its rod 53 and lever 26awith its slot 54, and when no recycling device or communication betweenthe compressor chambers of the auto-generators is provided. Recycling bymeans of slide-valve 34 in the device of FIG. 7 is controlled in such amanner that, due to it, the actual output of the autogenerators to theturbine is reduced as indicated by the shaded area, so as to conform tothe power-gas requirement of the turbine.

In all the installations which have just been described, it has beenassumed that the phase difference between the movements of the freepistons of the various autogenerators was fixed and equal to 180, whilethe free cross-section of the communication conduit 33 was assumed to bevariable, the resistance offered to the transfer of air from onecompressor chamber 2:: to the other depending upon said cross-section.

According to the present invention, however, the cross-section ofcommunication conduit 33 may be constant, While the phase difierencebetween the two autogenerators may be varied.

For example, by varying this phase difference between and 180, avariation in output can be obtained such as is illustrated in FIGS. 9a,9b and 9c, in each of which the diagram of compression in the compressorchamber of one of the auto-generators is designated by A, while thecorresponding diagram of the other auto-generator is designated by B.

According to FIG. 911, it is assumed that the two autogenerators areworking in phase, that is to say, the phase difference between them iszero. In this case, the pressure and output of each auto-generator arethose of two auto-generators, which have no connection between theircompressor chambers. The compressed air pressure and the output aremaximum. For a phase difference of 90 (FIG. 9b), the pressure and outputare already considerably reduced, and for a phase dilference of 180(FIG. 9c), the pressure and output are very small. In this case inparticular, the efiective pressures and outputs depend upon thecross-section of the communication between the connectedcompressorchambers, because if these crosssections were infinitely great, andconsequently the resistance to transfer is zero, the output of theconnectedcompressor chambers would drop to zero for this phasedifference of 180.

To produce the variation in phase difference between twoauto-generators, it is possible to use a device having a rotating arm38' and brushes 39-40 acting on the opening of valves 2t as shown inFIG. 1. To vary the phase difference between the generators, it is thenmerely necessary to vary, by a movement of at least one of the brushes39, 40, the angle having its apex at the centre of rotation of contactorarm 38 and the sides of which pass through brushes 39 and 40. The phasedifference between the autogenerators is equal to the value of thisangle.

Of course, it would also be possible simultaneously to vary the phasedifference between the autogenerators and the cross-section of theconduit or conduits 33 connecting compressor chambers 2a together.

It has repeatedly been stated in the foregoing that it is alwaysadvantageous to arrange the communication conduit 33 and its controlslide-valve 34 inside the suction casing so as to reduce the otherwisevery unpleasant noises which could be produced by the transfer of airunder pressure from one compressor chamber to the other. In the variousembodiments which have just been described, it has been assumed that onesingle suction casing is common to the compressor chambers connectedtogether by said communication conduit, and that during the startingperiod, escape of air is effected into this common casing. This directescape into the common casing has the great advantage of making a supplypipeline unnecessary. Furthermore, the air thus discharged into thecasing during the starting period serves to heat the two generators.

Of course, two separate casings could be provided, one for eachcompressor chamber. In this case, however, it would be advantageousnevertheless to provide a connection between these two casings.

When the two compressor chambers to be connected together bycommunication conduit 33 are at some dis.- tance from each other,thereby necessitating a certain length for conduit 33, it may beadvantageous to replace the single control member 34 by two controlmembers, controlled simultaneously, and each of which is in theimmediate vicinity of one of the two compressor chambers, in order thusto reduce the increase in clearance space for each compressor chamberdue to the fact that said clearance space includes the portion ofconduit 33 extending between said chamber and control member 34.

The communication between the compressor cylinders might be controlledby reciprocating means capable, during every working cycle of the freepistons, of opening and closing the communication between the compressorchambers and adjustable in such manner as to vary the duration ofopening of the communication conduit during one cycle. Of course thenumber of autogenerators having their compressor chambers connectedtogether by a transfer conduit may be greater than two.

In a general manner, while I have, in the above description, disclosedwhat I deem to be practical and efficient embodiments of my invention,it should be well understood that I do not wish to be limited thereto asthere might be changes made in the arrangement, disposition and form ofthe parts without departing from the principle of the present inventionas comprehended within the scope of the accompanying claims.

What I claim is:

1. An installation which comprises at least two autogenerators, each ofsaid auto-generators including a driving portion consisting of aninternal combustion engine, a compressor portion operatively connectedwith said driving portion so. as to be driven by it, said compressorportion including means forming a variable volume chamber, meansoperatively connected with both of said auto-generators for producing aphase difference between the respective cycles of operation of saidauto-generators, and means interposed between said two auto-generatorsfor establishing a permanent direct communication between the respectivevariable volume chambers of the respective compressor portions of saidauto-generators.

2. An installation according to claim 1 which further comprises meansfor controlling said communication means to vary the resistance offeredby said communication means to the transfer of air from one variablevolume chamber to the other.

3. An installation according to claiml in which said means for producingsaid phase difference are adjustable so as to permit of varying thevalue of said phase difierence.

4. An installation according to claim 1 in which said twoauto-generators have opposed cylinders and free pistons therein, and aredisposed in parallel relation to each other, said communication meansbeing provided between at least two compressor cylinders arranged at theadjacent ends of the two auto-generators, respectively.

5. An installation according to claim 1 which further comprises asuction casing surrounding the respective compressor portions of the twoauto-generators, said communication means being located in said suctioncasing.

6. An installation which comprises at least two autogenerators, each ofsaid auto-generators including a driving portion consisting of aninternal combustion engine, a compressor portion-operatively connectedwith said driving portion so as to be driven by it, said compressorportion including means forming a variable volume chamber, meansoperatively connected with both of said autogenerators for producing aphase difference between the respective cycles of operation of saidauto-generators,

means interposed between said two auto-generators for placing saidvariable volume chambers thereof respectively in communication with eachother, said communication means being provided with an orifice openinginto a space at a pressure at least approximately equal to atmosphericpressure, and valve means for controlling said orifice. I

7. An installation according to claim 6 in which said valve meansfurther constitutes means for controlling the cross-section area of flowthrough-said communication means.

8. An installation according to claim 6 in which said valve means is aslide-valve provided with a hole extending therethrough, saidslide-valve being capable, in a first position, to open said orificeleading to the surrounding space, in a second position to close thisopening but to open, by means of its hole, said communication meansbetween said variable volume cylinders and, in a third position, toclose said communication means.

9. An installation according to claim 2 in which said means forcontrolling said communication means is a control member adapted tooccupy only two positions, one for which it fully opens saidcommunication means and the other for which it fully closes saidcommunication means.

10. An installation according to'claim 2 further comprising means forregulating the quantity of fuel fed to said auto-generator drivingportions in response to variations of the pressure of the gas producedby said autogenerators.

References Cited in the file of this patent UNITED STATES PATENTS HuberJune 14, 1949

